1. Field of the Invention
The invention concerns a circuit for the suppression of interference pulses in transformers with a high leakage inductance. The transformers may typically supply a single consumer each by means of current controlled switches.
2. Description of the Prior Art
Suppression circuits are required for example in change-over control devices for slide projectors. It is known that change-over control devices may contain current controlled switches, such as TRIACs, which must be reignited after every voltage half-wave by means of a trigger, utilizing a control device. To generate these ignition pulses, the control device has its own transformer mains to supply the power.
However, it is sometimes desirable for reasons of simplification to supply the control devices from the illumination transformer already present in a projector. In such cases it is possible that interference pulses present at the instant of the switch ignition at the secondary winding of the transformer and caused by the high leakage inductance due to the particular design of most of these transformers, will actuate the trigger at the wrong time, thus significantly interfering with the synchronization of the control device.
Because such an interference pulse is capable of collapsing the secondary voltage to 0 volts, a simple filtering of the pulse by means of an RC element does not provide adequate suppression of the interference. Such a suppression is more critical the closer the interference pulse is located to the zero crossing of the alternating current voltage.